Battery module

ABSTRACT

Battery module includes: battery stack including a plurality of batteries that are stacked, each of the plurality of batteries having valve portion; duct plate configured to cover a first surface of battery stack on which a plurality of valve portions are disposed, duct plate having gas discharge duct that temporarily stores a gas blown off from valve portions of respective batteries; cover plate placed on duct plate; flow path portion defined by duct plate and cover plate, flow path portion being connected to gas discharge duct through opening, flow path portion extending in a first direction that intersects with stacking direction of the batteries, flow path portion allowing leaking of the gas in gas discharge duct to an outside of battery module; and gas restricting wall portion disposed in gas discharge duct between valve portion and opening.

TECHNICAL FIELD

The present invention relates to a battery module.

BACKGROUND ART

For example, as a power source for a vehicle or the like that requires ahigh output voltage, there has been known a battery module formed byelectrically connecting a plurality of batteries to each other. Ingeneral, each of the batteries that form the battery module is providedwith a valve portion that opens in response to an increase in innerpressure. For example, when a short circuit occurs in the battery sothat the temperature rises, a gas is generated by a chemical reaction inthe battery. As a result, when the inner pressure in the batteryincreases, a gas having a high temperature and a high pressure is blownoff from the valve portion. With respect to a battery module includingsuch batteries, PTL 1 discloses a battery module which includes: abattery stack in which a plurality of batteries are stacked; and a gasdischarge duct which is fixed to one surface of the battery stack insuch a manner that the gas discharge duct is connected to the valveportions of the respective batteries.

CITATION LIST Patent Literature

-   PTL 1: WO 2013/161655 A

SUMMARY OF THE INVENTION Technical Problems

When a gas that is blown off from the battery is discharged to theoutside of the battery module and is mixed with outside oxygen, there isa risk of the occurrence of fire outside the battery module. In order toensure safety of a user of the battery module, it is required to delaythe occurrence of fire outside the battery module for a predeterminedtime (for example, five minutes) after a gas is blown off. To satisfythis requirement, various countermeasures against occurrence of fire areapplied to the battery module.

As a method of suppressing the occurrence of fire outside the batterymodule, a method is considered where a gas blown off from a battery canbe gradually leaked to the outside of the battery module with asufficient time. As a result, the temperature of a gas or fine particlesblown off from the battery can be lowered so that the occurrence of fireoutside the battery module can be suppressed. On the other hand, inrecent years, battery modules are required to further increase theircapacities. In order to satisfy such requirement, the development ofbatteries having higher capacities has been in progress. When thecapacity of the battery increases, an amount of a gas blown off from thebattery increases. In the future, when a capacity of a battery furtherincreases so that an amount of a gas blown off from the battery furtherincreases, a risk that a fire occurs outside a battery module increasesso that the safety of a battery module may be lowered.

The present invention has been made in view of such circumstances, andit is an object of the present invention to provide a technique whichcan enhance safety of a battery module.

Solution to Problems

According to one aspect of the present invention, there is provided abattery module having the following configuration. The battery moduleincludes: a battery stack including a plurality of batteries that arestacked, each of the plurality of batteries having a valve portionthrough which a gas is blown off; a duct plate configured to cover afirst surface of the battery stack on which a plurality of the valveportions are disposed, the duct plate having a gas discharge duct thatextends in a stacking direction of the batteries, is connected to thevalve portions of the respective batteries, and temporarily stores ablown-off gas; a cover plate placed on the duct plate; a flow pathportion defined by the duct plate and the cover plate, the flow pathportion being connected to the gas discharge duct through an opening,the flow path portion extending from the gas discharge duct in a firstdirection that intersects with the stacking direction of the batteriesand allowing leaking of the gas in the gas discharge duct to an outsideof the battery module; and a gas restricting wall portion disposed inthe gas discharge duct between the valve portion and the opening, thegas restricting wall portion extending in a direction that intersectswith the first surface.

Any combinations of the above-described constituent elements, andconfigurations that are obtained by expressing the present invention inthe form of method, apparatus, system and the like are also effective asthe configuration of the present invention.

Advantageous Effects of Invention

According to the present invention, the safety of a battery module canbe enhanced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a battery module according to anexemplary embodiment.

FIG. 2 is an exploded perspective view of the battery module.

FIG. 3 is a cross-sectional side view of a region in which a duct plateand a cover plate of the battery module are disposed.

FIG. 4 is a cross-sectional side view of a region in which a duct plateand a cover plate of the battery module are disposed.

FIG. 5 is a cross-sectional view schematically illustrating a portion ofa battery module according to a first modification.

FIG. 6 is a cross-sectional view schematically illustrating a portion ofa battery module according to a second modification.

FIG. 7 is a cross-sectional view schematically illustrating a portion ofa battery module according to a third modification.

DESCRIPTION OF EMBODIMENT

Hereinafter, the present invention will be described based on apreferred exemplary embodiment with reference to the drawings. Theexemplary embodiment is an exemplification and does not limit theinvention. All technical features described in the exemplary embodimentand combinations of these technical features are not always essential tothe invention. The same reference symbols are assigned to the identicalor equivalent constituent elements, members and processes illustrated inthe respective drawings. Repeated explanation of the identical orequivalent constituent elements, members, and processes is omitted whennecessary. Scales or shapes of respective portions illustrated in therespective drawings are set for convenience sake to facilitate thedescription of the portions. The scales or shapes of the portions shouldnot be construed as limitation unless otherwise specified. Further, in acase where terms such as “first”, “second”, and the like are used in thepresent description and claims, these terms do not mean any order or thedegree of importance unless otherwise specified, and are intended to beused to distinguish one configuration and another configuration fromeach other. Further, in each drawing, some members that are notimportant for describing the exemplary embodiment are omitted.

FIG. 1 is a perspective view of a battery module according to anexemplary embodiment. FIG. 2 is an exploded perspective view of thebattery module. In FIG. 2, the illustration of gas restricting wallportions 98 (see FIG. 3) is omitted. Battery module 1 includes batterystack 2, a pair of end plates 4, cooling plate 6, heat conductive layer8, side separators 10, constraining members 12, duct plate 28, and coverplate 60.

Battery stack 2 includes a plurality of batteries 14 and inter-cellseparators 16. Each battery 14 is a chargeable secondary battery such asa lithium ion battery, a nickel-hydrogen battery, or a nickel-cadmiumbattery, for example. Each battery 14 is a so-called prismatic battery,and has exterior can 18 having a flat rectangular parallelepiped shape.Exterior can 18 has a substantially rectangular opening not shown in thedrawings on one surface of exterior can 18. An electrode assembly, anelectrolyte and the like are housed in exterior can 18 through theopening. Sealing plate 20 that closes the opening of exterior can 18 isdisposed in the opening.

Output terminal 22 of a positive electrode is disposed on sealing plate20 at a position close to one end of sealing plate 20 in a longitudinaldirection, and output terminal 22 of a negative electrode is disposed onsealing plate 20 at a position close to the other end of sealing plate20 in the longitudinal direction. The pair of output terminals 22 isrespectively electrically connected to positive electrode plates andnegative electrode plates that form the electrode assembly. Hereinafter,output terminal 22 of the positive electrode is referred to as positiveelectrode terminal 22 a, and output terminal 22 of the negativeelectrode is referred to as negative electrode terminal 22 b asappropriate. When there is no need to distinguish polarities of outputterminals 22 from each other, positive electrode terminal 22 a andnegative electrode terminal 22 b are collectively referred to as outputterminals 22.

Exterior can 18, sealing plate 20, and output terminals 22 are electricconductors and are made of metal, for example. Sealing plate 20 and theopening of exterior can 18 are joined to each other by, for example,laser welding. Respective output terminals 22 are inserted into throughholes (not illustrated) formed in sealing plate 20. A seal member (notillustrated) having insulating property is interposed between respectiveoutput terminals 22 and respective through holes.

In the description of the present exemplary embodiment, for convenience,sealing plate 20 forms an upper surface of battery 14, and a bottomsurface of exterior can 18 disposed on a side opposite to sealing plate20 forms a lower surface of battery 14. Battery 14 has two main surfacesthat connect the upper surface and the lower surface of battery 14 toeach other. The main surfaces are surfaces that have the largest areaamong six surfaces of battery 14. The main surfaces are long sidesurfaces that are connected to long sides of the upper surface and longsides of the lower surface. Two remaining surfaces other than the uppersurface, the lower surface, and two main surfaces form side surfaces ofbattery 14. These side surfaces are a pair of short side surfaces thatare connected to short sides of the upper surface and short sides of thelower surface.

For convenience, in battery stack 2, upper surfaces of batteries 14 forman upper surface of battery stack 2, lower surfaces of batteries 14 forma lower surface of battery stack 2, and side surfaces of batteries 14form side surfaces of battery stack 2. These directions and positionsare defined for convenience. Therefore, for example, the portion definedas the upper surface in the present invention does not always mean thatthe portion defined as the upper surface is positioned above the portiondefined as the lower surface.

Valve portion 24 is disposed on sealing plate 20 between the pair ofoutput terminals 22. Valve portion 24 is also referred to as a safetyvalve. Valve portion 24 is a mechanism which allows each battery 14 toblow off a gas in battery 14. Valve portion 24 is configured to releasean internal gas by opening valve portion 24 when an inner pressure inexterior can 18 is increased to a predetermined value or more. Forexample, valve portion 24 is formed of; a thin wall portion that isformed on a portion of sealing plate 20 and is thinner than otherportions of valve portion 24; and a linear groove formed on a surface ofthe thin wall portion. In this configuration, when an inner pressure inexterior can 18 increases, the thin wall portion is torn using thegroove as a tearing starting point so that valve portion 24 is opened bytearing. Valve portions 24 of respective batteries 14 are connected togas discharge duct 38 described later, and a gas in the battery isdischarged from valve portion 24 to gas discharge duct 38.

Each battery 14 has insulating film 26. Insulating film 26 is, forexample, a cylindrical shrink tube, and is heated after exterior can 18is made to pass through insulating film 26. Accordingly, insulating film26 shrinks and covers two main surfaces, two side surfaces, and bottomsurface of exterior can 18. Insulating film 26 can prevent a shortcircuit between batteries 14 disposed adjacently to each other or ashort circuit between battery 14 and end plate 4 or constraining member12.

The plurality of batteries 14 are stacked to each other at apredetermined interval in a state where the main surfaces of batteries14 disposed adjacently to each other face each other. The term “stack”means that a plurality of members are arranged in any one direction.Therefore, stacking of batteries 14 also includes an arrangement of theplurality of batteries 14 in a horizontal direction. In the presentexemplary embodiment, batteries 14 are horizontally stacked.Accordingly, stacking direction X of batteries 14 is a directionextending horizontally. Hereinafter, when appropriate, a direction thatis horizontal and is perpendicular to stacking direction X is referredto as horizontal direction Y, and a direction that is perpendicular tostacking direction X and horizontal direction Y is referred to asvertical direction Z.

Respective batteries 14 are disposed in a state where output terminals22 are directed in the same direction. In the present exemplaryembodiment, respective batteries 14 are disposed in a state where outputterminals 22 are directed upward in the vertical direction. With respectto the respective batteries 14, when batteries 14 disposed adjacently toeach other are connected in series, batteries 14 are stacked in a statewhere positive electrode terminal 22 a of one battery 14 and negativeelectrode terminal 22 b of other battery 14 are disposed adjacently toeach other. When batteries 14 disposed adjacently to each other areconnected in parallel, batteries 14 are stacked to each other in a statewhere positive electrode terminal 22 a of one battery 14 and positiveelectrode terminal 22 a of other battery 14 are disposed adjacently toeach other.

Inter-cell separator 16 is also referred to as an insulating spacer, andis formed of a resin sheet having an insulating property, for example.As examples of the resin that are used for forming inter-cell separator16, thermoplastic resins such as polypropylene (PP), polybutyleneterephthalate (PBT), polycarbonate (PC), and Noryl (registeredtrademark) resin (modified PPE) are named. Inter-cell separator 16 isdisposed between two batteries 14 disposed adjacently to each other andelectrically insulates two batteries 14 from each other.

Battery stack 2 is sandwiched between the pair of end plates 4 instacking direction X of batteries 14. The pair of end plates 4 isdisposed at both ends of battery stack 2 in stacking direction X alongwhich batteries 14 are stacked. The pair of end plates 4 is disposedadjacently to batteries 14 positioned at both ends of battery stack 2 instacking direction X with external end separator 5 interposed betweenthe end plate 4 and battery 14. External end separator 5 can be made ofthe same resin material as inter-cell separator 16. Each end plate 4 isa metal plate made of metal such as iron, stainless steel, or aluminum.By interposing external end separator 5 between end plate 4 and battery14, end plate 4 and battery 14 are electrically insulated from eachother.

Each end plate 4 has fastening holes 4 a on two surfaces that aredirected in horizontal direction Y. In the present exemplary embodiment,three fastening holes 4 a are disposed at a predetermined interval invertical direction Z. The surface where fastening holes 4 a are formedfaces flat surface portion 54 of constraining member 12. Flat surfaceportion 54 will be described later.

Duct plate 28 is placed on the upper surface of battery stack 2. Ductplate 28 is a plate-shaped member that covers an upper surface ofbattery stack 2, that is, a first surface of battery stack 2 on whichvalve portions 24 of respective batteries 14 are disposed. Duct plate 28has a plurality of openings 32 through which valve portions 24 areexposed at positions corresponding to valve portions 24 formed onrespective batteries 14. The plurality of openings 32 are formed in baseplate 33 extending along the upper surface of battery stack 2. Ductplate 28 includes gas discharge duct 38 that temporarily stores the gasblown off from respective batteries 14. Gas discharge duct 38 extends instacking direction X of batteries 14 and is connected to valve portions24 of respective batteries 14. Respective valve portions 24 communicatewith gas discharge duct 38 through openings 32.

Gas discharge duct 38 is defined by: first wall portion 34 that coversthe upper sides of the plurality of openings 32; and a pair of secondwall portions 36 which surrounds the sides of respective openings 32.First wall portion 34 and the pair of second wall portions 36respectively have an elongated shape elongated in stacking direction X.The pair of second wall portions 36 is arranged in horizontal directionY with the plurality of openings 32 disposed between the second wallportions 36, and the respective wall surfaces of the pair of second wallportions 36 are directed in horizontal direction Y that intersects withstacking direction X of batteries 14. First wall portion 34 has a wallsurface that is directed in vertical direction Z along which duct plate28 and cover plate 60 are arranged, and faces respective valve portions24. The pair of second wall portions 36 protrudes from base plate 33toward cover plate 60, and forms both side surfaces of gas dischargeduct 38. First wall portion 34 is fixed to upper ends of the pair ofsecond wall portions 36 to form a top surface of gas discharge duct 38.

Duct plate 28 has openings 40 through which output terminals 22 areexposed at positions corresponding to output terminals 22 of respectivebatteries 14. Bus bars 42 are placed on respective openings 40. Theplurality of bus bars 42 are supported by duct plate 28. Accordingly,duct plate 28 also functions as a so-called bus bar plate. Bus bar 42placed in respective openings 40 electrically connects output terminals22 of batteries 14 disposed adjacently to each other.

Duct plate 28 of the present exemplary embodiment is made of a resinsuch as polypropylene (PP), polybutylene terephthalate (PBT),polycarbonate (PC), and Noryl (registered trademark) resin (modifiedPPE) except for first wall portion 34. First wall portion 34 is made ofmetal such as iron or aluminum. The pair of second wall portions 36 isintegrally formed with base plate 33 by molding. First wall portion 34is fixed to the pair of second wall portions 36 by fastening members(not illustrated) such as screws.

Bus bar 42 is a substantially strip-shaped member made of metal such ascopper or aluminum. One end portion of bus bar 42 is connected to outputterminal 22 of one battery 14, and the other end portion of bus bar 42is connected to output terminal 22 of another battery 14. With respectto bus bars 42, output terminals 22 having the same polarity in aplurality of batteries 14 disposed adjacently to each other may beconnected in parallel by bus bars 42 to form a battery block, and thesebattery blocks may be connected in series by bus bars 42.

Bus bars 42 connected to output terminals 22 of batteries 14 positionedat both ends in stacking direction X each have external connectionterminal 44. External connection terminal 44 is connected to an externalload (not illustrated). Voltage detection line 46 is placed on ductplate 28. Voltage detection line 46 is electrically connected to theplurality of batteries 14 to detect voltages of respective batteries 14.Voltage detection line 46 includes a plurality of conductive wires (notillustrated). One end of each conductive wire is connected to each busbar 42, and the other end is connected to connector 48. Connector 48 isconnected to an external battery ECU (not illustrated) or the like.Battery ECU controls detection of a voltage or the like of each battery14, charging and discharging of each battery 14, and the like.

Cooling plate 6 has a flat plate shape extending in stacking direction Xand in horizontal direction Y, and is made of a material having highthermal conductivity such as aluminum. Cooling plate 6 is thermallyconnected to battery stack 2. That is, cooling plate 6 is connected tobattery stack 2 in a heat-exchangeable manner, and cools respectivebatteries 14. In the present exemplary embodiment, battery stack 2 isplaced on a main surface of cooling plate 6. Battery stack 2 is placedon cooling plate 6 in a state where a lower surface of battery stack 2faces a cooling plate 6. Accordingly, battery stack 2 and cooling plate6 are arranged in vertical direction Z. Cooling plate 6 may be connectedto an object disposed outside of battery module 1, for example, avehicle body of a vehicle on which battery module 1 is mounted or thelike in a heat-exchangeable manner. A flow path through which arefrigerant such as water or ethylene glycol flows may be disposed incooling plate 6. With such a configuration, heat exchange efficiencybetween battery stack 2 and cooling plate 6 can be further enhanced and,eventually, cooling efficiency of batteries 14 can be further enhanced.

Heat conductive layer 8 is a member having an insulating property whichis interposed between battery stack 2 and cooling plate 6. That is,cooling plate 6 is thermally connected to battery stack 2 by way of heatconductive layer 8. Heat conductive layer 8 covers the entire bottomsurface of battery stack 2. The thermal conductivity of heat conductivelayer 8 is higher than the thermal conductivity of air. Heat conductivelayer 8 can be formed of, for example, a known resin sheet having goodthermal conductivity, such as an acrylic rubber sheet or a siliconerubber sheet. In addition, heat conductive layer 8 may be made of aknown adhesive agent, grease, or the like having favorable thermalconductivity and favorable insulating property. When exterior can 18 issufficiently insulated by insulating film 26 or the like, heatconductive layer 8 may not have insulating property.

By interposing heat conductive layer 8 between battery stack 2 andcooling plate 6, thermal connection between respective batteries 14 andcooling plate 6 can be more reliably obtained. Therefore, the coolingefficiency of respective batteries 14 can be enhanced, and respectivebatteries 14 can be more uniformly cooled. In a case where heatconductive layer 8 has an insulating property, it is possible to preventbattery stack 2 and cooling plate 6 from being electrically connected toeach other with more certainty. Heat conductive layer 8 can suppressdisplacement between battery stack 2 and cooling plate 6.

Side separators 10 are members that have an insulating property andinsulate constraining members 12 and battery stack 2 from each other. Inthe present exemplary embodiment, the pair of side separators 10 isarranged in horizontal direction Y. Each side separator 10 has anelongated shape elongated in stacking direction X of batteries 14.Battery stack 2, the pair of end plates 4, cooling plate 6, and heatconductive layer 8 are disposed between the pair of side separators 10.Each side separator 10 is made of, for example, a resin having aninsulating property. As a resin that is used for forming side separator10, in the same manner as inter-cell separator 16, thermoplastic resinssuch as polypropylene (PP), polybutylene terephthalate (PBT),polycarbonate (PC), and Noryl (registered trademark) resin (modifiedPPE) are named.

Side separator 10 of the present exemplary embodiment has first portion50, second portion 52, and third portion 53. First portion 50 has arectangular flat plate shape, and extends in stacking direction X ofbatteries 14 along a side surface of battery stack 2. Second portion 52has a strip shape extending in stacking direction X, and protrudes froma lower side of first portion 50 toward a battery stack 2. Third portion53 has a strip shape extending in stacking direction X, and protrudesfrom an upper side of first portion 50 toward the battery stack 2.Accordingly, second portion 52 and third portion 53 face each other inthe arrangement direction of battery stack 2 and cooling plate 6.Battery stack 2, cooling plate 6, and heat conductive layer 8 aredisposed between second portion 52 and third portion 53.

Constraining members 12 are also referred to as bind bars, and areelongated members that are elongated in stacking direction X ofbatteries 14. In the present exemplary embodiment, the pair ofconstraining members 12 is arranged in horizontal direction Y. Eachconstraining member 12 is made of metal. As examples of metal used forforming constraining member 12, iron, stainless steel, and the like arenamed. Battery stack 2, the pair of end plates 4, cooling plate 6, heatconductive layer 8, and the pair of side separators 10 are disposedbetween the pair of constraining members 12.

In the present exemplary embodiment, constraining member 12 includesflat surface portion 54 and a pair of arm portions 56. Flat surfaceportion 54 has a rectangular shape, and extends in stacking direction Xalong the side surface of battery stack 2. The pair of arm portions 56protrude toward a battery stack 2 from end portions of flat surfaceportion 54 on both sides in vertical direction Z. That is, one armportion 56 protrudes from an upper side of flat surface portion 54toward the battery stack 2, and the other arm portion 56 protrudes froma lower side of flat surface portion 54 toward the battery stack 2.Accordingly, the pair of arm portions 56 faces each other in thearrangement direction that battery stack 2 and cooling plate 6 arearranged. Battery stack 2, cooling plate 6, heat conductive layer 8, andside separators 10 are disposed between the pair of arm portions 56.

Contact plate 68 is fixed to regions of flat surface portion 54 thatface respective end plates 4 by welding or the like. Contact plates 68are members that are elongated in vertical direction Z. Through holes 70are formed in contact plate 68 in a penetrating manner in horizontaldirection Y at positions that correspond to fastening holes 4 a formedin end plate 4. Through holes 58 are formed in flat surface portion 54in a penetrating manner in horizontal direction Y at positions thatcorrespond to through holes 70 formed in contact plate 68.

By making the pair of end plates 4 engage with flat surface portions 54of respective constraining members 12, the plurality of batteries 14 aresandwiched between end plates 4 in stacking direction X. Specifically,battery stack 2 is formed by alternately arranging the plurality ofbatteries 14 and the plurality of inter-cell separators 16, and suchbattery stack 2 is sandwiched between the pair of end plates 4 withexternal end separators 5 sandwiched between battery stack 2 and endplates 4 in stacking direction X. Heat conductive layer 8 is disposedbelow the lower surface of battery stack 2 and, further, cooling plate 6is disposed so as to face battery stack 2 with heat conductive layer 8interposed between cooling plate 6 and battery stack 2. In such a state,battery stack 2, the pair of end plates 4, cooling plate 6, and heatconductive layer 8 are sandwiched between the pair of side separators 10in horizontal direction Y. Further, the pair of constraining members 12sandwiches the whole body in horizontal direction Y from the outside ofthe pair of side separators 10.

The pair of end plates 4 and the pair of constraining members 12 arealigned with each other in a state where fastening holes 4 a, throughholes 70, and through holes 58 overlap with each other. Fasteningmembers 59 such as screws are made to pass through through holes 58 andthrough holes 70 and are made to threadedly engage with fastening holes4 a. With such a configuration, the pair of end plates 4 and the pair ofconstraining members 12 are fixed to each other. By making the pair ofend plates 4 and the pair of constraining members 12 engage with eachother, the plurality of batteries 14 are fastened to each other and areconstrained in stacking direction X. Accordingly, respective batteries14 are positioned in stacking direction X.

Constraining members 12 sandwich the plurality of batteries 14 instacking direction X. Constraining members 12 also sandwich batterystack 2, heat conductive layer 8, and cooling plate 6 in the arrangementdirection of battery stack 2, heat conductive layer 8, and cooling plate6. Specifically, constraining members 12 sandwich the plurality ofbatteries 14 in stacking direction X in such a manner that both endportions of flat surface portions 54 of constraining members 12 instacking direction X of batteries 14 engage with the pair of end plates4. Battery stack 2, heat conductive layer 8, and cooling plate 6 aresandwiched between the pair of arm portions 56 of constraining members12 in vertical direction Z. That is, constraining members 12 have both afunction of fastening the plurality of batteries 14 and a function offastening battery stack 2 and cooling plate 6. Therefore, unlike theconventional structure, battery stack 2 and cooling plate 6 are notfastened by screws.

In a state where the pair of constraining members 12 is fixed to thepair of end plates 4, first portion 50 of side separator 10 isinterposed between the side surface of battery stack 2 and flat surfaceportion 54 of constraining member 12. With such a configuration, theside surfaces of respective batteries 14 and flat surface portion 54 areelectrically insulated from each other. Second portion 52 of sideseparator 10 is interposed between cooling plate 6 and arm portion 56 ona lower side of constraining member 12. With such a configuration,cooling plate 6 and arm portion 56 on the lower side are electricallyinsulated from each other. Third portion 53 of side separator 10 isinterposed between the upper surface of battery stack 2 and arm portion56 on an upper side of constraining member 12. With such aconfiguration, the upper surfaces of respective batteries 14 and armportion 56 on the upper side are electrically insulated from each other.

In a state where battery stack 2, heat conductive layer 8, and coolingplate 6 are sandwiched by the pair of arm portions 56 in verticaldirection Z, heat conductive layer 8 is elastically deformed orplastically deformed by being pressed by battery stack 2 and coolingplate 6. Consequently, it is possible to obtain thermal connectionbetween battery stack 2 and cooling plate 6 with more certainty. Inaddition, entire battery stack 2 can be cooled uniformly. Further,deviation between battery stack 2 and cooling plate 6 in the XY planedirection can be further suppressed. The XY plane direction is adirection that expands in stacking direction X and in horizontaldirection Y.

As an example, after assembling of these constituent elements iscompleted, duct plate 28 is placed on battery stack 2. Duct plate 28 isfixed to battery stack 2 by making third portions 53 of the pair of sideseparators 10 engage with duct plate 28. Then, bus bars 42 are mountedon output terminals 22 of respective batteries 14 so that outputterminals 22 of the plurality of batteries 14 are electrically connectedto each other. For example, bus bars 42 are fixed to output terminals 22by welding.

Cover plate 60 is placed on an upper surface of duct plate 28. Coverplate 60 is a plate-shaped member that covers duct plate 28 from above.Cover plate 60 according to the present exemplary embodiment is aso-called top cover that forms a portion of an outer shell of batterymodule 1, specifically, the upper surface of battery module 1. Coverplate 60 prevents dew condensation water, dust, or the like from beingbrought into contact with output terminals 22, valve portions 24 ofbatteries 14, bus bars 42 and the like. Cover plate 60 is made of aresin having an insulating property such as, for example, polypropylene(PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl(registered trademark) resin (modified PPE). Cover plate 60 hasinsulating cover portions 62 at position overlapping with externalconnection terminals 44 in vertical direction Z. In a state where coverplate 60 is placed on duct plate 28, external connection terminals 44are covered by insulating cover portions 62.

Both end portions of cover plate 60 in horizontal direction Y are fixedto duct plate 28. Cover plate 60 of the present exemplary embodiment isfixed to duct plate 28 by snap-fitting. Specifically, duct plate 28 hasa plurality of engaging claws 72 at both end portions of duct plate 28in horizontal direction Y in a state where the plurality of engagingclaws 72 are disposed at an interval in stacking direction X. Coverplate 60 has engaging holes 74 at positions overlapping with respectiveengaging claws 72 when viewed in vertical direction Z. When cover plate60 is placed on duct plate 28, each engaging claw 72 is inserted intoeach engaging hole 74. With such insertion of engaging claws 72, bothend portions of cover plate 60 in horizontal direction Y are fixed toduct plate 28.

FIG. 3 is a cross-sectional side view of a region in which duct plate 28and cover plate 60 of battery module 1 are disposed. FIG. 4 is across-sectional side view of a region in which duct plate 28 and coverplate 60 of battery module 1 are disposed. FIG. 3 illustrates a crosssection along a YZ plane expanding in horizontal direction Y and invertical direction Z. FIG. 4 illustrates a cross section along an XZplane expanding in stacking direction X and in vertical direction Z. InFIG. 3 and FIG. 4, the illustration of an internal structure of battery14 is omitted.

Battery module 1 includes flow path portions 76. Flow path portions 76are flow paths that allow a gas in gas discharge duct 38 to leak to theoutside of battery module 1. Flow path portions 76 are defined by ductplate 28 and cover plate 60, and extend from gas discharge duct 38 inthe first direction (horizontal direction Y in the present exemplaryembodiment) intersecting with stacking direction X. In the presentexemplary embodiment, flow path portions 76 are disposed on both sidesin horizontal direction Y with gas discharge duct 38 sandwiched betweenflow path portions 76. Respective flow path portions 76 are connected tosecond wall portions 36 directed in horizontal direction Y of gasdischarge duct 38. More specifically, opening 78 is formed in each ofsecond wall portions 36, and one end portion of each of flow pathportions 76 is connected to opening 78. Therefore, flow path portions 76are connected to gas discharge duct 38 through openings 78. The otherend portions of respective flow path portions 76 are connected to flowpath outlets 80 disposed at the end portions of battery module 1 inhorizontal direction Y.

The plurality of openings 78 are formed in second wall portion 36 at apredetermined interval in stacking direction X, and one end portion offlow path portion 76 is connected to the plurality of openings 78. Flowpath outlet 80 is an opening that is elongated in stacking direction X.Therefore, flow path portion 76 is a planar flow path that expands instacking direction X and horizontal direction Y. Cover plate 60 isdisposed in a state where predetermined gap G is formed between coverplate 60 and first wall portion 34 of gas discharge duct 38. That is,first wall portion 34 and cover plate 60 are spaced apart from eachother in vertical direction Z by gap G. Both end portions of gap G inhorizontal direction Y are connected to flow path portions 76.Therefore, two flow path portions 76 arranged in horizontal direction Ycommunicate with each other through gap G.

When a gas in battery 14 is blown off from valve portion 24, the gasimpinges on first wall portion 34 which face valve portion 24. The gasthat impinges on first wall portion 34 flows along first wall portion 34and flows into flow path portions 76 through openings 78. The gasflowing into flow path portions 76 flows through flow path portions 76in horizontal direction Y and in stacking direction X, and leaks fromflow path outlets 80 to the outside of battery module 1.

At least a portion of the gas blown off from battery 14 is a combustiblegas. The gas blown off from battery 14 also contains fine particles suchas broken pieces of a battery structure. When a combustible gas having ahigh temperature and fine particles having a high temperature aredischarged to the outside of battery module 1, and these gas or fineparticles are mixed with oxygen outside the module, there is a risk thatfire may occur outside battery module 1. On the other hand, in thepresent exemplary embodiment, a gas blown off from valve portion 24 isonce received by gas discharge duct 38 and then, is gradually dischargedto the outside of battery module 1 through flow path portions 76. As aresult, a temperature of a gas or fine particles can be lowered beforethe gas or the fine particles are released to the outside of batterymodule 1. Accordingly, the occurrence of fire outside battery module 1can be suppressed.

Battery module 1 also includes gas restricting wall portions 98 whichare disposed between valve portions 24 and openings 78 in gas dischargeduct 38. Gas restricting wall portions 98 extend in a direction thatintersects with the first surface of battery stack 2 on which valveportions 24 are disposed. With such a configuration, gas restrictingwall portion 98 can restrict straight-forward movement of a gas fromvalve portion 24 to opening 78. Gas restricting wall portion 98 isdisposed at least between each valve portion 24 and opening 78 closestto each valve portion 24.

In the present exemplary embodiment, gas restricting wall portion 98 hasa tubular shape that surrounds an entire circumference of opening 32formed in duct plate 28, and protrudes in vertical direction Z from aperipheral portion around each opening 32. Respective gas restrictingwall portions 98 are integrally formed with base plate 33 by molding.Therefore, lower ends of gas restricting wall portions 98 are connectedto base plate 33. A gap is formed between an upper end of gasrestricting wall portion 98 and first wall portion 34.

A gas blown off from valve portion 24 is restricted from movement instacking direction X and horizontal direction Y by gas restricting wallportion 98. That is, the gas is guided toward first wall portion 34 bygas restricting wall portion 98 and impinges on first wall portion 34.Thereafter, the gas expands in gas discharge duct 38 in the XY planedirection from the gap formed between the upper end of gas restrictingwall portion 98 and first wall portion 34.

As has been described above, battery module 1 according to the presentexemplary embodiment includes: battery stack 2 having the plurality ofbatteries 14 that are stacked; duct plate 28 placed on battery stack 2;cover plate 60 placed on duct plate 28; flow path portions 76 defined byduct plate 28 and cover plate 60; and gas restricting wall portions 98.Each of the plurality of batteries 14 of battery stack 2 has valveportion 24 through which a gas is blown off. Duct plate 28 includes gasdischarge duct 38, and covers the first surface of battery stack 2 onwhich the plurality of valve portions 24 are disposed. Gas dischargeduct 38 extends in stacking direction X of batteries 14, is connected tovalve portions 24 of respective batteries 14, and temporarily stores ablown-off gas. Flow path portions 76 are connected to gas discharge duct38 through openings 78, extend from gas discharge duct 38 in the firstdirection that intersects with stacking direction X of batteries 14, andmakes a gas in gas discharge duct 38 leak out to the outside of batterymodule 1. Gas restricting wall portions 98 are disposed in gas dischargeduct 38 between valve portions 24 and openings 78, and extend in adirection that intersects with the first surface of battery stack 2 soas to restrict straight-forward movement of a gas from valve portions 24to openings 78.

By connecting respective valve portions 24 to gas discharge duct 38, gasdischarge duct 38 can receive an impact and a pressure of a blown-offgas. In particular, gas discharge duct 38 can receive a large impact ora rapidly rising pressure generated at an initial stage of blowing offof a gas. A gas blown off to gas discharge duct 38 gradually leaks tothe outside of battery module 1 through flow path portions 76.Accordingly, it is possible to prevent a gas from being vigorously blownoff to the outside of battery module 1. In addition, by allowing a gasgradually leak through flow path portions 76, a temperature of the gasor fine particles can be lowered until the gas or the fine particlesreach flow path outlets 80. With such a configuration, it is possible tosuppress the occurrence of fire outside battery module 1.

Battery module 1 according to the present exemplary embodiment includesgas restricting wall portions 98. It is naturally estimated that a gasgenerated in battery 14 is blown off in a right upward direction fromvalve portion 24. However, as a result of intensive studies thatinventors of the present invention have made, the inventors have foundthat, contrary to their estimation, a direction that a gas is blown offchanges with a lapse of time. Therefore, there may be a case where a gasgenerated in battery 14 moves straight forward toward opening 78 fromvalve portion 24 rather than toward first wall portion 34 from valveportion 24 at least temporarily.

In this case, the gas blown off from valve portion 24 and fine particlescontained in the gas immediately flow out into flow path portion 76without staying in gas discharge duct 38. When an amount of a gas blownoff from battery 14 increases along with a demand for an increase ofcapacity of battery 14, an amount of a gas and fine particles that areblown off from valve portion 24 and move straight forward toward opening78 increases. Accordingly, the gas and the fine particles are leaked tothe outside of battery module 1 while being maintained at a hightemperature and hence, a possibility of the occurrence of fire outsidebattery module 1 increases.

On the other hand, in the present exemplary embodiment, gas restrictingwall portions 98 are provided so as to restrict the straight-forwardmovement of a gas toward opening 78 from valve portion 24. With such aconfiguration, it is possible to make a gas blown off from valve portion24 stay in gas discharge duct 38 with more certainty. Accordingly, it ispossible to suppress leaking of the gas and the fine particles to theoutside of battery module 1 while being maintained at a hightemperature. Therefore, according to the present exemplary embodiment,safety of battery module 1 can be enhanced. In addition, it is possibleto increase the capacity of battery module 1 while maintaining thesafety of battery module 1.

In addition, an amount of a gas and fine particles that move straightforward from valve portion 24 to opening 78 is reduced by providing gasrestricting wall portion 98. Accordingly, compared with a case where anamount of a gas and fine particles that move straight forward from valveportion 24 to opening 78 is reduced by increasing a volume of gasdischarge duct 38, it is possible to suppress the large-sizing ofbattery module 1.

The exemplary embodiment of the present invention has been described indetail heretofore. The above-described exemplary embodiment is merely aspecific example for carrying out the present invention. The contents ofthe exemplary embodiment do not limit the technical scope of the presentinvention, and many design changes such as changes, additions, anddeletions of constituent elements can be made without departing from thespirit of the invention defined in claims. Novel exemplary embodimentswith a design change acquire both advantageous effects of the exemplaryembodiment and the modification that are combined with each other. Inthe above-described exemplary embodiment, with respect to the contentswhere such design changes are allowable, the contents are emphasizedwith expressions such as “of the present exemplary embodiment” and “inthe present exemplary embodiment”. However, the design changes areallowable even with respect to the contents which are not emphasizedwith such expressions. Any arbitrary combination of constituent elementsincluded in the exemplary embodiment is also effective as theconfiguration of the present invention. Hatching applied to the crosssections in the drawings does not limit materials of objects to whichhatching is applied.

(First Modification)

FIG. 5 is a cross-sectional view schematically illustrating a portion ofbattery module 1 according to a first modification. In FIG. 5, theillustration of an internal structure of battery 14 is omitted. Inbattery module 1 according to the present modification, gas restrictingwall portion 98 is formed such that end portion 98 a of gas restrictingwall portion 98 close to duct plate 28 is disposed at a position awayfrom valve portion 24 by a predetermined interval I in an in-planedirection of a plane orthogonal to a second direction (verticaldirection Z in the present modification) along which duct plate 28 andcover plate 60 are arranged (a direction that an XY plane expands in thepresent modification).

Gas restricting wall portion 98 is inclined from a duct plate 28 sidetoward a cover plate 60 side so as to be closer to valve portion 24 asviewed in the second direction along which duct plate 28 and cover plate60 are arranged. That is, gas restricting wall portion 98 is formed suchthat end portion 98 b of gas restricting wall portion 98 near coverplate 60 is positioned closer to valve portion 24 in the in-planedirection of the XY plane than end portion 98 a near duct plate 28.

In the present modification, gas restricting wall portion 98 is formedof a sleeve that has an elliptical truncated conical shape and surroundsthe entire circumference of opening 32 formed in duct plate 28. Gasrestricting wall portion 98 that is closer to the duct plate 28 sidethan the cover plate 60 expands in the XY plane direction. Therefore,catching pocket 100 defined by base plate 33 and gas restricting wallportion 98 is formed on a peripheral portion around opening 32. Catchingpocket 100 is a space formed by: a surface of base plate 33 facing coverplate 60 at a peripheral portion around opening 32; and an inclinedinner surface of gas restricting wall portion 98.

When a gas is blown off from valve portion 24, a portion of fineparticles contained in the gas impinges on the inner surface of gasrestricting wall portion 98 so that the portion of fine particles iscaught by catching pocket 100. With such a configuration, diffusion offine particles contained in the gas blown off from valve portion 24 canbe suppressed and hence, an amount of fine particles flowing into flowpath portion 76 can be reduced. Therefore, leaking of fine particles tothe outside of battery module 1 can be suppressed and hence, theoccurrence of fire outside the module can be further suppressed. Inaddition, since the fine particles and the gas can be separated fromeach other, a temperature of the gas can be lowered more quickly.Therefore, the occurrence of fire outside the module can be furthersuppressed.

(Second Modification)

FIG. 6 is a cross-sectional view schematically illustrating a portion ofbattery module 1 according to a second modification. In FIG. 6, theillustration of an internal structure of battery 14 is omitted. Inbattery module 1 of the present modification, gas restricting wallportion 98 overlaps with at least a portion of valve portion 24 asviewed in a second direction (vertical direction Z in the presentmodification) along which duct plate 28 and cover plate 60 are arranged.The gas restricting wall portion 98 of the present modification includespartition portion 102 and eaves portion 104. Partition portion 102protrudes in vertical direction Z from an edge portion of opening 32.Eaves portion 104 extends in the in-plane direction of an XY plane froman upper end of partition portion 102, and covers entire valve portion24 just above valve portion 24.

Since eaves portion 104 covers at least a portion of valve portion 24,diffusion of fine particles contained in a gas blown off from valveportion 24 can be suppressed, and an amount of fine particles flowinginto flow path portion 76 can be reduced. As a result, leaking of fineparticles to the outside of battery module 1 can be suppressed andhence, the occurrence of fire outside the module can be furthersuppressed.

In the present modification, gas restricting wall portion 98 is formedsuch that a region of a peripheral portion around valve portion 24 thatdoes not intersect with imaginary line L connecting opening 78 closestto valve portion 24 and the valve portion 24 is opened in an in-planedirection of a plane orthogonal to the second direction (in the presentmodification, an expanding direction of the XY plane). As an example,partition portion 102 is disposed in a region that intersects with theimaginary line L, and open port 106 is formed in a region positionedopposite to the region with valve portion 24 sandwiched by the regions.Imaginary line L is, for example, a straight line connecting a geometriccenter of contour shape of open port 106 and a geometric center of acontour shape of valve portion 24. In a case where opening 78 isdisposed on both sides of valve portion 24 in horizontal direction Y,open port 106 is formed in a region directed in stacking direction X. Itmay be construed that imaginary line L corresponds to a path along whicha gas moves straight forward from valve portion 24 toward opening 78.

In this manner, by forming open port 106 in the region which does notface opening 78 disposed closest to valve portion 24, the blow-offdirection of a gas from valve portion 24 can be directed to the regionremote from opening 78. As a result, a gas blown off from valve portion24 can be made to stay in gas discharge duct 38 with more certainty.Therefore, the occurrence of fire outside battery module 1 can befurther suppressed.

(Third Modification)

FIG. 7 is a cross-sectional view schematically illustrating a portion ofbattery module 1 according to a third modification. In FIG. 7, theillustration of the internal structure of battery 14, inter-cellseparator 16, and opening 78 is omitted. In battery module 1 accordingto the present modification, gas restricting wall portions 98 areinclined from a duct plate 28 toward a cover plate 60 so as to be closercenter C of battery module 1 as viewed in a second direction (verticaldirection Z in the present modification) along which duct plate 28 andcover plate 60 are arranged. Center C of battery module 1 is a center inan in-plane direction of an XY plane orthogonal to vertical direction Z.That is, gas restricting wall portions 98 are configured such that endportion 98 b of each gas restricting wall portion 98 on a cover plate 60side is positioned closer to center C of battery module 1 than endportion 98 a of each gas restricting wall portion 98 on a duct plate 28side in the in-plane direction of the XY plane.

Center C of battery module 1 generally has higher rigidity in ductstructure than rigidity in duct structure of a peripheral portion ofbattery module 1. Therefore, by directing a blow-off direction of a gasfrom valve portion 24 toward center C of battery module 1, it ispossible to reduce a risk that gas discharge duct 38 is damaged by thegas blown off from valve portion 24. Therefore, the safety of batterymodule 1 can be further enhanced.

(Others)

In the exemplary embodiment and the modifications, the gas restrictingwall portions 98 are formed on the duct plate 28. However, the presentinvention is not particularly limited to such configuration, and gasrestricting wall portion 98 may be formed on cover plate 60. The numberof batteries 14 that battery module 1 includes is not particularlylimited. The structures of respective parts of battery module 1including the shape of side separator 10 and the fastening structurebetween end plates 4 and constraining members 12 are not particularlylimited. Battery 14 may have a cylindrical shape or the like. In a casewhere both heat conduction and a frictional force can be sufficientlyensured between battery stack 2 and cooling plate 6, heat conductivelayer 8 may be omitted, and an insulating sheet made of PET or PC may beinterposed between battery stack 2 and cooling plate 6.

REFERENCE MARKS IN THE DRAWINGS

-   -   1: battery module    -   2: battery stack    -   14: battery    -   24: valve portion    -   28: duct plate    -   38: gas discharge duct    -   60: cover plate    -   76: flow path portion    -   78: opening    -   98: gas restricting wall portion

1. A battery module comprising: a battery stack including a plurality ofbatteries that are stacked, the plurality of batteries including valvesthrough which a gas is blown off; a duct plate configured to cover afirst surface of the battery stack, the duct plate being disposed thevalves, the duct plate including a gas discharge duct that extends in astacking direction of the batteries, is connected to the valves of thebatteries, and temporarily stores the gas blown off through the valves;a cover plate placed on the duct plate; a flow path defined by the ductplate and the cover plate, the flow path being connected to the gasdischarge duct through an opening, the flow path extending from the gasdischarge duct in a first direction that intersects with the stackingdirection of the batteries, the flow path allowing leaking of the gas inthe gas discharge duct to an outside of the battery module; and a gasrestricting wall disposed in the gas discharge duct and between thevalve and the opening, the gas restricting wall extending in a directionthat intersects with the first surface.
 2. The battery module accordingto claim 1, wherein the gas restricting wall includes an end close to aduct plate at a position away from the valve by a predetermined intervalin an in-plane direction of a plane orthogonal to a second directionalong which the duct plate and the cover plate are arranged, and the gasrestricting wall is inclined closer to the valve near the cover platethan near the duct plate as viewed in the second direction.
 3. Thebattery module according to claim 1, wherein the gas restricting walloverlaps with at least a part of the valve as viewed in a seconddirection along which the duct plate and the cover plate are arranged.4. The battery module according to claim 3, wherein the gas restrictingwall includes a region of a peripheral part around the valve that doesnot intersect with an imaginary line connecting the opening closest tothe valve and the region is opened in an in-plane direction of a planeorthogonal to the second direction.
 5. The battery module according toclaim 1, wherein the gas restricting wall is inclined closer to a centerof the battery module near the cover plate than near the duct plate asviewed in a second direction along which the duct plate and the coverplate are arranged.